Compliant hydrodynamic fluid bearings are potentially usable in virtually every bearing application which exists today. Techniques are available for extremely low cost mass production of these bearings, and their performance capabilities are potentially superior to those of conventional bearings used today. However, difficulties exist with the application of these bearings and these difficulties have delayed their full acceptance and utilization by the art.
One difficulty with conventional hydrodynamic compliant fluid bearings is that they are usually unidirectional. This is because the bearing sheet tends to wrap around the rotating shaft and grip the shaft in the manner of a railroad band break. Attempts at preventing this problem by anchoring the free end of the bearing sheet have proven unsuccessful because it prevents the necessary freedom of motion that the bearing sheet must have to provide the necessary hydrodynamic effect.
Another difficulty with conventional fluid bearings is that the start-up torque is frequently quite high. It is believed that one reason for this difficulty is that the bearing sheet which is loose at one end is free to relax inwardly and lie flush against the shaft around the full 360.degree. circumference. As a consequence, this large surface contact represents a substantial frictional resistance to the initiation of rotation of the shaft and, in some applications, actually prevents the rotor from starting at all.
Another tenacious problem in this art is that of bearing stability. Hydrodynamic fluid journal bearings in particular frequently exhibit various instability phenomena, of which the most difficult to solve has been the half-speed whirl phenomenon. Various solutions have been attempted to overcome this problem, but it still persists to some extent to this day. This invention contributes to the solution of this problem by improved damping. By circumferentially loading the bearing sheet in compression, snug contact is induced between the bearing sheet and support element, and between the support element and the bearing sleeve. This greatly enhances the damping effect of the bearing and tends to absorb the whirl energy and lessen the peak displacement of the shaft at the otherwise destructive phase of this phenomenon.
Other additional advantages have been obtained by this invention. For example, the improved alignment of the tape and supporting element with each other and the bearing sleeve fixes the lightly loaded bearing clearance to a specific value and also tends to promote retention of the bearing elements within the bearing sleeve, or, to put it the other way, prevent the spiraling of the bearing elements out of the bearing sleeve.